In order to meet the needs of high-density host access of a data center, a vertical virtualization technology becomes more popular. A stacking system built by the vertical virtualization technology typically includes a core backbone (CB) device and a port extender (PE) device. In a stacking system, each PE device is connected to a CB device. From the point view of logical level, a PE device can be understood as a remote line card of a CB device. A CB device is connected to a plurality of PE devices, and each PE device may provide a plurality of access ports, so that the entire the stacking system may provide more access ports, and have good scalability.